The present invention relates generally to improved techniques for capturing of barcode information. More particularly, the invention relates to methods and apparatus for use of a user selection device such as a multiposition switch to select among possible scan patterns and to selectively inhibit decoding in a multimode scanner.
A barcode signal is typically produced by passing or scanning a laser beam across a barcode. The laser beam traces a pattern into which the barcode is introduced, and the light reflected from the barcode as the scanner traces across the barcode is captured to produce a photosignal which is decoded to extract barcode information. Depending on the expected use of a barcode scanner and the nature of the barcodes likely to be presented to the scanner, different patterns may be selected for use. A scanner may be designed to employ a particular pattern, or may be designed to allow selection from a variety of patterns. The most common patterns employed are an omnidirectional pattern and a single line pattern. An omnidirectional pattern is most convenient for use when a single barcode is to be brought within the field of view of the scanner and involves the tracing of a two dimensional pattern by the laser. When a barcode is brought within this pattern, recognition and decoding occur quickly. It is not necessary to position the barcode precisely in order to enable the scanner to recognize the barcode. However, an omnidirectional pattern is not suitable for decoding one of a group of barcodes occurring in close proximity to one another, because it is not possible to isolate the pattern to the area of a single barcode.
A single line pattern involves the tracing of the laser back and forth in one dimension, so that the pattern appears as a straight line. A straight line pattern can be more easily aligned to a defined area than can an omnidirectional pattern, so that it is possible to decode a barcode occurring in proximity to other barcodes.
Barcode scanners of the prior art suffer from a significant limitation when presented with a need to decode a barcode occurring in close proximity to other barcodes. Scanners are typically active to capture and decode a barcode as soon as the barcode comes within a scanner pattern. Even in the case of a single line pattern, the correct barcode must be aligned with the pattern in order to be scanned. In the case of a single line pattern, the operator typically needs to see the pattern in order to align it with a barcode. If other barcodes occur near the desired barcode, the scanner pattern may fall on one of the other barcodes before the operator is able to align it with the desired barcode. This can result in detection and decoding of one of the other, undesired barcodes resulting in a need for the operator to delete the false reading or, if the operator fails to notice that a false reading was made, an error resulting from the false reading.
There exists, therefore, a need in the art for a barcode scanner which will allow an operator to align a scan pattern with a desired barcode and which will allow decoding to be inhibited until alignment is achieved.
A barcode scanner according to one aspect of the present invention includes a scanner engine which produces either a presentation scan or a single line scan according to an operator selection. The scanner also includes a photodiode for converting reflected light into a photosignal and a decoding circuit for decoding the photosignal to extract barcode information. The decoding circuit communicates with a processor which directs the operation of the scanner engine and the decoding of the barcode signal and use of the barcode information. The scanner also includes a user selection device connected to the processor for providing operator selection information to the processor. As an example, the user selection device may be implemented as a pushbutton with a first position which may be characterized as a released position, a second position which may be characterized as a first pressed position at a stop in an intermediate position in the range of travel of the pushbutton, and a third position which may be characterized as a second pressed position at the end of the range of travel of the pushbutton. If the pushbutton is in a released position, the scanner engine produces an omnidirectional scan. If the pushbutton is in a first pressed position, the scanner produces a single line scan and the processor inhibits decode of a barcode. If the pushbutton is in a second pressed position, the scanner produces a single line scan and the processor decodes a barcode aligned with the scan pattern. In this way the pushbutton may be moved to the first pressed position to allow the scanner to produce a scan pattern which can be aligned with a desired barcode, but without a danger of decoding a barcode for which decoding is not desired while alignment is taking place. Once a satisfactory alignment has been made, the pushbutton can be moved to the second pressed position to allow decoding.
A more complete understanding of the present invention, as well as further features and advantages of the invention, will be apparent from the following Detailed Description and the accompanying drawings.